Quasicrystals, crystals and multiple twins in rapidly solidified Al-Cr-Si, Al-Mn-Si and Al-Mn-Cr-Si alloys

Journal Article · Mon Jul 01 04:00:00 EDT 1996 · Acta Materialia

DOI:https://doi.org/10.1016/1359-6454(95)00353-3· OSTI ID:264110

Srivastava, A K; Ranganathan, S ^[1]

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1. Indian Inst. of Science, Bangalore (India)

The coexistence of quasicrystals and rational approximant structures (RAS) has been observed in melt-spun Al{sub 80}Cr{sub 14}Si{sub 6}, Al{sub 80}Mn{sub 14}Si{sub 6} and Al{sub 75}Mn{sub 10}Cr{sub 5}Si{sub 10} alloys. The presence of a b.c.c. {alpha}-AlMnSi phase in Al-Mn-Si and {alpha}-AlMnSi(Cr) phase in Al-Mn-Cr-Si has been seen. A multiple twinning around an irrational axis of the RAS has been reported in an aggregate of fine size cubic crystallites in all three alloys. Selected area diffraction patterns show that the crystalline aggregate symmetry is linked to the icosahedral point group symmetry (m{ovr 35}). Various ways of expressing the twin relationship in the cubic crystalline aggregates have been discussed. The thermal stability of the icosahedral phase at high temperatures reveals that the icosahedral phase in Al-Mn-Si and Al-Mn-Cr-Si alloys transforms to {alpha}-AlMnSi at temperatures of 690 and 670 K, respectively. In Al-Cr-Si alloy, heating to a high temperature (615 K) leads to the transformation of the icosahedral phase into a new metastable phase having an ordered cubic structure equivalent to {alpha}-AlMnSi. The occurrence of multiple twinning leading to icosahedral symmetry in the as-spun Al-Cr-Si alloy is presumably due to this metastable phase.

• OSTI ID: 264110
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Journal Issue: 7 Vol. 44; ISSN XZ504Y; ISSN 1359-6454
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AGGLOMERATION
ALUMINIUM ALLOYS
CHROMIUM ALLOYS
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
CUBIC LATTICES
ELECTRON DIFFRACTION
INTERMETALLIC COMPOUNDS
MANGANESE ALLOYS
METASTABLE STATES
SILICON ALLOYS
TEMPERATURE DEPENDENCE
TWINNING